The present invention relates to a waveguide type optical switch that is employed in the field of optical communication, and more particularly to a waveguide type optical switch which is small in size and suitable for remote control.
Among conventional waveguide type optical switches is a 1xc3x972 optical switch disclosed in Japanese Patent Unexamined Publication No. 6-148536. This 1xc3x972 optical switch has a cantilever beam formed on a silicon substrate, and serves to perform optical path switching by moving an optical waveguide formed on the cantilever beam with the use of electrostatic force.
In the aforementioned optical switch the following points have not been taken into consideration.
First, the use of electrostatic force requires the drive volt is as high as tens of volts or more, and a single-cantilever beam structure for the optical switch involves turning of a tip end of the waveguide concurrently with translating motion at the time of optical switching operation, which causes non-parallelism of the optical entrance plane and optical exit plane of the waveguide, leading to an increased loss of insertion. In addition, a substrate is formed of silicon, and so if silica glass is used as a material for the optical waveguide, the waveguide will be distorted or cracked due to a difference between the linear expansion coefficients of the both components.
It is an object of the present invention to solve the above problems and provide a waveguide type optical switch which can be driven with a voltage of 10 volts or less and which is small in insertion loss and low in cost.
To achieve this end, an optical waveguide switch according to the present invention comprises a silica glass substrate; a plurality of cantilever beams formed in parallel to one another on the silica glass substrate, and connected at their tip ends to a connection member; at least one input silica glass optical waveguide core formed on the cantilever beams; a plurality of output optical waveguide cores fixed in opposition to the input silica glass optical waveguide core; and switch drive means for bending the cantilever beams.
Further, the invention provides an optical switch for switching an optical path of an input optical signal, comprising a silica glass substrate, a separation layer formed on the silica glass substrate, a plurality of cantilever beams formed in parallel to one another on the separation layer, and connected at their tip ends to a connection member, at least one input silica glass optical waveguide core formed on the cantilever beams, a plurality of output optical waveguide cores fixed in opposition to the input silica glass optical waveguide core, and switch drive means for bending the cantilever beams.
The thickness of the separation layer is less than a height of the input optical waveguide core, and at least one of the connection member or those members on the substrate which are disposed to be brought into contact with the connection member when an optical-path switching operation is performed are recessed in a movement direction of the connection member.
The switch drive means comprises soft magnetic bodies provided on the connection member for the cantilever beams and on the substrate, and an electromagnetic actuator comprising a soft magnetic yoke provided on the substrate and formed of a soft magnetic body, a permanent magnet, and a wire coil.
The soft magnetic yoke is divided to form an interior yoke formed of a soft magnetic body, and an exterior yoke formed of a soft magnetic body and opposed to the interior yoke through a cover formed with an insertion hole for an index regulating liquid.
With the above arrangement, a plurality of cantilever beams formed in parallel to one another and connected at their tip ends to the connection member function to have their tip ends moved parallel with one another when an optical-path switching operation is performed.
Therefore, the tip end portions of the optical waveguides formed on the cantilever beams are also moved parallel with one another upon the optical-path switching operation. This parallel movement of the optical waveguides makes selection of an output optical waveguide to enable optical path switching.
In the present invention, the silica glass optical waveguides are formed on a silica glass substrate, which can make the difference in liner expansion coefficient between the substrate and the optical waveguide layer extremely small, and consequently it is possible to suppress warp and deformation of the substrate and cantilever beams to accurately position the optical waveguides on the emergent and incident sides.
In the present invention, the separation layer provided on the whole or part of the silica glass substrate is removed by etching, and so movable cantilever beams separated from the substrate can be obtained with ease and in a short time.
In the present invention, a press member fixed to the substrate crosses at least one of the tip ends of the cantilever beams, and so there is no possibility that the cantilever beams will be separated from the substrate in a vertical direction.
In the present invention, the cover for covering the whole of cantilever beams allows an index regulating liquid to fill around the cantilever beams and their vicinities and eliminates the possibility of adherence of foreign matters which may hinder a switching operation, and so high reliable switching can be performed.
In the present invention, the thickness of the separation layer is less than the height of the optical waveguide, and so even if there were any positional discrepancy equivalent to the gap between the silica glass substrate and the cantilever beam after removal of the separation layer, there would be no possibility that the ends of the facing optical waveguides were completely displaced from each other and therefore the optical coupling would be maintained. Accordingly, even in the case where the cantilever beam is displaced by external disturbance, an extreme reduction in the optical coupling efficiency can be suppressed.
In the present invention, at least one of the connection member or those members on the substrate which are disposed to be brought into contact with the connection member when an optical-path switching operation is performed are recessed in a movement direction of the connection member to thereby limit the contact area to a small magnitude. Furthermore, it is possible to suppress the index regulating liquid from entering portions, with which the connection member and the aforementioned member on the substrate contact, to form a gap therebetween.
In the present invention, magnetic forces are generated between the soft magnetic body formed on the connection member for cantilever beams and above the substrate, and wire coils and the permanent magnet, and can be utilized to deform the cantilever beam to thereby switch the optical waveguide formed on the cantilever beam.
Further, in the present invention, the soft magnetic yoke formed of a soft magnetic body and constituting a part of a magnetic circuit can be divided to provide an interior yoke formed of a soft magnetic body and provided on the substrate, and an exterior yoke formed of a soft magnetic body and opposed to the interior yoke with the cover therebetween, so that it is possible to form only the interior yoke inside the cover enclosing the entire cantilever beam and the exterior yoke outside the cover. With this arrangement, the wire coil and the permanent magnet are not received within the cover, so the cover can be reduced in size and also foreign matters possibly produced from the permanent magnet and the wire coil can be prevented from adhering to the cantilever beam and their vicinities.
Further objects and advantages of the present invention will become apparent from the following detailed description when read in conjunction with the accompanying drawings.